• Computational Structural Engineering
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• v.9 no.2
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• pp.103-113
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• 1996

This paper presents practical notional-load plastic-hinge method for a two-dimensional steel structure design. The proposed method incorporates the refined plastic-hinge concept for spread of plasticity together with a practical notional-load approach. The proposed method can assess realistically both strength and behavior of a structural system and its individual members in a direct manner. As a result, the method can be used for design without tedious separate member capacity checks, including the calculation of K-factor. The strengths predicted by the proposed method are then compared with those predicted by the exact plastic-zone analysis as well as by the conventional LRFD procedure. A good agreement is generally observed. The displacement predictions are compared with the plastic-zone solutions. Analysis and design guidelines in using the proporsed method are given in detail. Analysis and design procedures are recommended. Member sizes determined by the proposed method are compared with those determined by the LRFD method. It is concluded that the procedures are suitable for adoption in practice.

• Journal of the Korean Magnetics Society
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• v.22 no.2
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• pp.66-72
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• 2012

The findings of ferromagnetic superconductor have attracted much attention not only for fundamental research to investigate how the antagonistic properties of ferromagnetism and superconductivity coexist peacefully but also for potential technological applications. Firstly, in order to help for understanding the ferromagnetic superconductor, I have explained the orbital and paramagnetic pair-breaking effects of magnetic field, which breaks the superconducting Cooper pairs. In addition to such effects of magnetic field, the singlet Cooper pairs become unstable upon going through the ferromagnetic materials by the proximity effect. The proximity effect occurs at the interface of thin films composing of superconductor and ferromagnet and leads to have very short penetration depth of Cooper pairs. However, a type of odd-frequency triplet in comparison with the singlet could be very stable and has a longer effective depth. It needs to be explored for the innovative spintronic devices. Finally, various ferromagnetic superconductors coexist and the lower-dimensional materials under the Quantum confinement effect have been introduced.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.9
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• pp.1991-1998
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• 2015

This paper presents the antenna factor characteristics of a calculable dipole antenna with a hybrid balun, installed above ground plane vertically and horizontally, using Method of Moments (MoM). An expression for the antenna factor is formulated using the concept of power mismatch loss. The input impedance and effective length of the antenna, which are in the formula of the antenna factor, are calculated using the MoM. The results show that the antenna factors above a ground plane are agreed with the free space antenna factors within ± 0.14 dB. The horizontal antenna factors are varied more by 0.2 dB than the vertical antenna factors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1542-1548
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• 2009

This paper describes a size-reduced Wilkinson power divider using substrate integrated artificial dielectric(SIAD). SIAD transmission lines have increased effective refractive index, so the line width and length are reduced from those of standard transmission lines. Therefore the "size-reduction effect" is achieved if SIAD lines are applied to high frequency circuits. An efficient simulation method is proposed for SIAD lines which have an enormous number of via-holes. A 2GHz Wilkinson power divider is designed and measured using SIAD transmission line as an example of application. The size of the fabricated divider is reduced by 32% due to the increased effective refractive index of SIAD, while the performances are maintained similarly.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.81-92
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• 2008

Generally the connection of members is defined as hinge or rigid. But, real joints on structure have to be considered semi-rigid connections because this permits relative rotation for members on joints. The purpose of this study is to derive a generalized tangential stiffness matrix of frames with semi-rigid connections and to develop a buckling analysis program. For the exact stiffness matrix, an accurate displacement field is introduced using an equilibrium equation for beam-columns under the bending and axial forces. Also, stability functions that consider sway deformation and force-displacement relations with rotational spring on ends were defined. In order to illustrate the accuracy of this study and the characteristics of semi-rigid for system buckling load, samples of angle-, portal- and 3-story frames with semi-rigid connections are presented, where the proposed approach is found to be in excellent agreement with other research results. Meanwhile, the application of codes such as Eurocode 3 and LRFD led to significant inaccuracies.

• Journal of Advanced Navigation Technology
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• v.17 no.6
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• pp.720-725
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• 2013

This paper has presented that fringing-electric fields enhanced by a finger-type electrode can improve the tunability of the tunable capacitor. Its top electrodes with different area and line width are designed in types of the finger for a long conducting perimeter. The tunable varactors were fabricated on a quartz substrate employing a multi-layer dielectric of a para/ferro/para-electric thin film. Compared to the conventional capacitor, finger-type capacitors are analyzed in terms of effective capacitance and tunablility. Their effective capacitance and tunability of the varactors with the long perimeter increase 24~40 % and 7~12 %, respectively, due to enhanced fringing electric fields from 1 to 2.5 GHz.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4D
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• pp.595-601
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• 2011

There is currently applied to the unit cost per a distance (KRW/km) for estimating the conceptual cost of civil work on basic planning stage of high speed railroad. This unit cost is an arithmetic average value based on historical data, which could be in big error. It also is difficult to explain the deficiency comparing the estimated cost derived from next basic design stage. This study provides the conceptual estimation model using by the parametric method and regression analysis. Independent variables are the distance and the geological materials (earth, weathered rock, soft-rock, hard-rock), extracting from the actual data to 36 contracts. The deviation between the unit costs estimated using the developed model and the actual cost data is presented in the range from -0.4% to +31%. This range is acceptable compared the typical range "-30% to + 50%". This model will improve the accuracy of existing method and be expected to contribute to effective total cost management and the economic aspects, reduce the financial expenditure.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.2
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• pp.235-243
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• 2012

In this paper, we propose a method to improve performance of pilot symbol assisted modulation(PSAM) channel estimation method for OFDM systems over frequency selective channel. When channel values are estimated, the low pilot density used for channel estimation increases not only the effective data rate but also power efficiency. Thus, the lower pilot density which is used for channel estimation is better for OFDM system. At first, we estimate the channel values which are located at the middle of adjacent pilots, and then all of the possible channel values are estiamted by using original pilot values and previously estimated pilot values. Furthermore, the error of estimated channel values is reduced by introducing guard interval which is designed acccording to maximum channel delay. Performance achieved with the proposed method is illustrated by simulation experiments in comparison with the existing methods in terms of mean squared error(MSE).

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.1
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• pp.101-107
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• 2013

Is generated in real time in the real world, a large amount of time series data from a wide range of business areas. But it is not easy to determine the optimal model for the description and understanding of the time series data is represented as a dynamic feature. In this study, through the HMM suitable for estimating the short and long-term forecasting model of time-series data to estimate a model that can explain the characteristics of these time series data, it was estimated to predict future patterns of movement. The actual stock market through various materials, information criterion and optimal model estimation for the length of the most efficient data was found to accurately estimate the state of the model. Similar movement patterns predictive than the long-term prediction is more similar to the short-term prediction of the experimental result were found to be.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.1
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• pp.11-17
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• 2007

Effects of combustion chamber design on combustion stability characteristics of a full-scale gas generator were studied experimentally. Thirty seven double-swirl injectors with recess number of 1.5 were distributed in the injector head, which significantly influences combustion performance. The characteristics of combustion stability were inspected by the parametric variations such as changing length and diameter of the combustion chamber and installing a turbulence ring. The experimental result shows that as the effective length of the combustion chamber decreased, an instability frequency took place in a high-frequency region, and the amplitude of the dynamic pressure generally diminished and could be reduced to the unharmful level. However, the dynamic pressure fluctuation in the region of longitudinal resonant frequency could not be suppressed perfectly.